This invention relates generally to cement product making machinery and more particularly to a method and apparatus for high speed manufacturing of a wide variety of high quality products.
Prior art machines for forming concrete products include a product forming section comprising a stationary frame, an upper compression beam and a lower stripper beam. A mold box has a head assembly which is mounted on the compression beam, and a mold assembly which is mounted on the frame and receives concrete material from a feed drawer. A conveyer system feeds metal pallets to the product forming section.
The head assembly raises above the mold assembly when the compression beam moves vertically upward into a raised position. After the compression beam raises, the stripper beam raises thereby placing a pallet against a bottom side of the mold assembly. The pallet seals the bottom side of cavities in the mold assembly. The feed drawer moves concrete material over the top of the mold assembly and dispenses the material into the contoured cavities.
As the concrete material is dispensed, a vibration system shakes the mold assembly. The vibration system spreads the concrete material evenly within the mold assembly cavities to produce a more homogeneous concrete product.
After the concrete is dispensed into the mold cavities, the feed drawer retracts from over the top of the mold assembly. The compression beam lowers pushing shoes from the head assembly into corresponding cavities in the mold assembly. The shoes compress the concrete material. After compression is complete, the stripper beam lowers as the head assembly pushes further into the cavities against the molded material. A molded concrete product thereby emerges from the bottom of the mold assembly onto the pallet. The pallet then moves via conveyer from the product forming section.
Several problems occur with the above stated product forming process. As the vibrator system shakes the mold assembly, the rest of the product forming machine also shakes. Machine vibration tends to dampen vibration in the mold assembly. Thus, concrete material in the mold box does not spread evenly in the mold assembly. Machine vibration also fatigues machine parts and alters the clearances between the head assembly and mold assembly. Thus, machine and mold box operating life is reduced and product quality is limited and furthermore deteriorates with machine use.
Mold boxes of various sizes are constantly exchanged in the product forming machine to produce different product shapes. When a new mold box is mounted in the machine, the various moving parts of the machine such as attachments to the compression and stripper beams, must be realigned. Realignment is necessary so that the machine can properly engage mold boxes of different heights. The head assembly and the mold assembly must also be jimmied until properly aligned together. Thus, a significant amount of time is required to properly mount and align a new mold box in the product forming machine. Machine down time while changing mold boxes reduces overall product output.
Pallets are located in a receiving position under the mold assembly by pushing pallets end-to-end. Sliding the pallets into a receiving position incurs wear on the pallet and increases the overall cycle time of the machine. For example, the time required to push a pallet into the receiving position increases because the pallet speed must be slowed down as the pallet approaches the receiving position.
Further, as the feed drawer dispenses concrete material into the mold assembly, a certain amount of concrete material accumulates on the topside of the mold assembly. As concrete further accumulates on the front edge, concrete material begins to spill off a front edge of the mold assembly.
Accordingly, a need remains for a high output concrete product forming machine that produces a wide variety of high quality products.